The proposed research represents a multifaceted study of the substantia and the striatum. Rather than studying the processing of information within these structures we will concentrate on the outputs: the effects of systemic drugs and of electrolytic and chemical lesions of the rotation (circling behavior) evoked by electrical stimulation of substantia nigra, and on the firing of antidromically identified efferent neurons of the caudate-putamen. Of particular interest are drugs which act at dopaminergic, cholinergic, gabaergic, and noradrenergic synapses. All studies will be done in rats.